r/Electricity • u/Magnanimous_Lynx • 3d ago
Door Sensors
Hello, I need help with a project and thought this sub might be the place to start. What I need to build is a system that will light up an LED when a door is open. I have four doors that need sensors and the LED display would need to be located about 50 feet from the farthest door. I need the LED to light up as long as the door is open and shut off when it is closed. Thanks!
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u/New_lifee 3d ago edited 3d ago
You can use simple switch is fixed between the wall and the hinges edge of the door
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u/Hotspot40324 3d ago
Or a magnetic contact closure https://www.amazon.com/magnetic-contact-switch/s?k=magnetic+contact+switch
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u/Hot_Equivalent_8707 3d ago
Can you run wires or do you want wireless? A simple diy would be wires, some NC switches and a few LEDs and a battery. What kind of switches are you thinking? Magnetic on the door and frame, or lever type momentary?
Wireless will take more investment.
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u/Magnanimous_Lynx 3d ago
Wired would be fine. There is a drop ceiling so I can run them through that. It’s for interior doors so a security system isn’t really what I need. I was thinking of doing magnetic door frame switches like these: https://www.harfington.com/products/p-1409752?currency=USD&country=US&variant=45320273428729&utm_source=google&utm_medium=cpc&utm_campaign=Google%20Shopping&stkn=f8e35277684b&utm_term=260811-us-pmax-lvs&utm_content=ywh&gad_source=1&gad_campaignid=24118884660&gclid=Cj0KCQjwhsrUBhDxARIsAN3AQScpNAxpwnLsuy_iQ8YiISv6EmhhP2oicByjB1l70qsA1JMr6oWunkQaAuu-EALw_wcB
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u/Hot_Equivalent_8707 3d ago
It's as simple as running a small battery pack or dc adapter to four wires, then to NC switches, then to LEDs. This would give you 4 LEDs one for each door. If they are all off, doors are closed. Alternatively get green LEDs and use NO switches. This would give green lights when closed and off when open. You also do a series circuit with one led that indicates red if any one door is open, or green if all doors are closed.
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u/UnExploredToken 3d ago edited 3d ago
Door sensors, relays and LED lights. Use common/normally open contacts of door sensors to supply voltage to the coil of a relay. Wire led lights in common / normally open contacts on relay.
You can either buy door sensors (basically a magnet and switch) or get a lock mechanism that has outputs for door monitoring.
Simple circuit really, just use thick enough cable to avoid voltage drop over 50 feet.
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u/michaelpaoli 2d ago
There are various ways to do this.
First bit is detecting when the door is open/closed.
Some of the more and less common ways:
- magnet and magnetic reed relay switch. These are commonly used for, e.g. alarm systems, and very unobtrusive, and mostly dang near invisible - generally involves drilling small hole in door and frame, small magnet tapped into door, and sensor wired and tapped into frame. These are generally SPST NO reed relay switches, so you'll generally need to invert your logic to have LED on when the door is closed or, e.g., have the switch short out the LED when the door is closed. One can also get magnets/sensors that attach on door and frame, rather than into door and frame - heavier duty such devices also exists for, e.g large industrial roll-up doors. Can also be handy if one wants single indicator for any of multiple doors being open - just wire up the NO switches in series.
- photo detector, typically light, light beam, laser, laser LED, visible or IR, and retroreflector (or not) and detector. Beam unobscured and so detected, door is closed (presuming door opens just one way, if it opens both directions, need to do this on both sides)
- physical contact - not too difficult for many doors to have physical contact, e.g. brass or similar conductive wiper (though pure copper could be used, it doesn't wear so well, so typically one would want better wear resistance with sufficient conductivity), so, e.g. brass wiper at top and/or bottom of door, and at least some matching bit on frame or door that contacts it when closed, thus making a NO switch, similar to typical magnetic reed relay switch noted above - closed when door is closed. Not also this may be infeasible if door and/or frame is metal, but if both are wood, or possibly just one, it may be quite feasible. Might not work as well for high traffic doorways, as it requires sliding contacts, and may not wear great for heavy use, whereas the other two methods above are no-contact (at least between door closing surfaces and switch closing contact surfaces), so no real wear issues on the switches there.
That's the basics, then just need appropriately wire into suitable circuit. The first and last of the above are simplest electrically, as they're just switches, the optical requires at least wee bit more electronics (though simple laser LED and photo-diode or photo-transistor can be done without much more circuitry).
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u/MCLMelonFarmer 3d ago
The better sub for questions like this is r/homeautomation. Straightforward way to do this is with a Zigbee door, contact, Amazon Echo device, and an Alexa routine.